import cv2
import matplotlib.pyplot as plt
image=cv2.imread("flower.png")
hist0=cv2.calcHist([image],[0],None,[256],[0,255])
hist1=cv2.calcHist([image],[1],None,[256],[0,255])
hist2=cv2.calcHist([image],[2],None,[256],[0,255])
plt.plot(hist0,color='b',linestyle='-')
plt.plot(hist1,color='g',linestyle=':')
plt.plot(hist2,color='r',linestyle='-.')
plt.show()